This research will be the first systematic investigation of significant change events in psychotherapy. Significant psychotherapy events are those moments which stand out for cleints and therapists as strikingly helpful or hindering in accomplishing psychological change in clients. This investigation differs from previous studies in that it focuses on particular observable significant events, obtains client and therapist subjective views of these events (via tape-assisted recall) and validates these subjective views with objective psychotherapy process measures. A series of systematic case studies wil be conducted focusing on several important current approaches, including Cognitive and Interpersonal Therapies of depression. The research will test and build on specific clinical theories about essential ingredients in psychotherapy for the purpose of providing an empirical base for the moment-to-moment conduct of psychotherapy. Such an empirical base would be uniquely useful for training professional and paraprofessional helpers. This project is also conceived of as a demonstration project for a oarger collaborative study of significant events in psychotherapy.